Means for cutting projecting gear teeth



0 8 1952 s. Q COOK Em 2 615 359 MEANS FOR CUTTING PROJECTING GEAR TEETH Filed Nov. 27. 1946 5 Sheets-Sheet 1 \fnswzsy 5/1/77? 620A laws Wear/M5,? 04 16-166 Oct. 28, 1952 s. s. COOK ETAL 2,615,359

MEANS FOR CUTTING PROJECTING GEAR TEETH Filed Nov. 27, 1946 5 Sheets-Sheet 2 ATTdF/VfVS Oct. 28, 1952 s. s. cooK ET AL 7 2,615,359

MEANS FOR CUTTING PROJECTING GEAR TEETH Filed Nov. 27, 1946 5 Sheets-Sheet s S. S. COOK ETAL MEANS FOR CUTTING PROJECTING GEAR TEETH.

Oct. 28, 1952 5 Sheets-Sheet 4 Filed Nov. 27, 1946 f N m 46 0 m r N/ T A L1 5 MW Z W M5 Oct. 28, 1952 s. s. COOK ETAL 7 2,615,359-

MEANS FOR CUTTING PROJECTING GEAR TEETH Filed Nov. 27, 194's s Sheets-Sheet s M VE/VTOFS Patented Oct. 28, 1952 TEETH Stanley SmithCook-and Louis Morti ernon sh Wallsend-on-Tyne Englandnassignors :to, :Ihe v 7 Parsons Marine Steam'Turbine Company, Limited; wallsend -oneT-yne, England Application-November 2'7,

In Great Britain September .14;l945

Section 1, Public Law s90; Au ust 8, 194 s Patent"expires"September 14, 1965 "This invention relates to means'for cutting internally projecting gear teeth of concave in-' volute form. Kinematically correct transmission of motion is attainable when such teeth-engage externally. projecting convex involute teeth 'havf ing the'sameba'sic pitch; that is, the same pitch of the 'involutes. The concave involute teeth on the'ring' having the internally projecting teeth;

cannot be generated'with the conventional type tion to the axis; 7 knownias the Fellows? Shaper process; in which acutter having theform of apinion'with convex involute teeth is reciprocatedalong its'axis to cut the teeth lengthwise and the teeth ofthe'workf are generated by rotating the cutter and the work so that they have the same circumferential speed at the pitch point.

The cutter cantbe made of any diameter up to the diameter-of thework itselfbut it is usually made much smaller for convenience;

Theintermittentmotion of this process is dis- I advantageous as 1 compared with the continuous uninterrupted motion of the hobbing process,f and'the object of the inventionis to produce a cutter or hob by which the concaveinvolutes of internally projecting teeth can'fbe formed. bythe' continuous-motion process known: as hobbing. In accordancewith the present inventiorrthe hob employed maybe of thetype inwhichthe' teethfllie atequal intervals along a, helical path around the hub circumference with the result that the successive cutting, edges cut at equal intervals in succession along the line of action;

The" invention consists in machines for producing hobs as Xset'forth in the claims appended hereto.

Referring to the accompanying. diagrainmatic,

drawingsp i Figure 1' illustrates'an involute toothed pinion engaging conjugate inwardly projecting teeth of a ring.

Figure 2 'is a sectional: sa anna; view 'of a hob constructed in accordancewith' thepresent:

invention.

measured along lines tangential tothe base circles" 3 -Claims.. (or-se m);

of'hob, the teeth or which are all of-thesame pitch'and the same'relative' disposition in rela'-= They'can' be formed by whatis' files and are equally pitched along that'tangent," that is, they have the samebasic pitch c'. That. isto say, in planes containing the axis of the hob" a's'in the upper partfof' Figure 2, the cutting" edges have the same form'and' disposition'as'thosez Figure 3is'a oross sectional viewthereof on the line 3-3 of FigureiZ. Figure 4 is a side elevational view partly in section of one form of machine in accordance with the present'invention forproducing a hob Y such aspillustratedin Figureszi and13.)

Fi ure 5 is a, planview partly machineofFigure4."

eie e i efj e 1946, Serial No. 7 12,6426

Figures is I a 'partplan view thereof.

Figure 7 is mainlya transverse section through a planet-l of Figure 5.

Figure 8 is a plan view of part of Fi'gure'h;

showingpartsbelowthe line 8-8 thereof.

Figure 9 is a partlongitudinal sectional View thereof, and is taken on the line 9-9 of Figure 7;

Figure 10 is a plan'view of part of Figure 91 Figure llis a part transverse sectional view. showing details of 'themechanismas viewed from the right of Figure 6.

Figure 12 is an end view, looking from'the lefti of Figure 5.

Figure =l3' isa view clearly details of theinternal' gearing;

Figure 14 s a :detail view showing the cam 36 5 of Figure 4 in profile;

Figure 15-is a section on Figure 4'; and- I Figure l6 is'a detail section on the'lineJB-Qfi I of Figure 4.

the-two sets ofteth.

A" suitable hob for cutting teeth internally pro. jecting from a ring such as. the-ringfeofFigure -'1 which/will produce true concave involutes' is! shown in Figures 2 and 3. The cutting edges: 72; areall 'offa similar convex involute form disposed I o'n a helical path around the circumference of the hob'and so orientated that in planes.containing the axis of "the hob they lie normally to the tangents ofthebase circle'of the involute proof a pinioniin a plane "transverse toits axis, such aspiniOn a; in Figure 1;

Preferablyth'e" cutting edges or teethfoffthe hob are equally spaced along the helicallpath on.

which they lie,

M ho

"e', igu'rei; if properly disposed relatively thereto;

7 imme Figure 12 buti with the cover plate of head stock 4 and-parts: outside the same removed so as tosh'ow more the-line lli-l5 of In'Figure 1 isillustrated a pinion (or cutter) a withconvex involute teethb having the samebasic pitch c-as theconcave involute teeth 11 ofra ring e 'and when these two elements rotate in; the same direction and at the same circumferen'ei tial speed at the pitch point p the contact oer- 1 tween the'engaging teeth movesuniformlyalongi the lines-of action It eachzof which is'partof the: common tangent to thebase circles ,f, and g-of I w as abovedescribed will produceconjugate: concaye involutegteeth, suchasd in a ring such theangular pitch of the flutes or gashes I'I.

reasonably small for convenience of manufacture and operation.

A modified form of hob may be employed for cutting gear teeth having a helical angle difierent from that of the hub thread wherein the profiles and disposition of the hob teeth in a plane through the axis of the hob is a projection through the appropriate angle of a section through an involute toothed pinion engaging the work, the said section being in a plane transverse to the axis of the work.

One construction of machine embodying the present invention for producing hobs as above described is illustrated in Figures 4-16 in which the work (hob) I is mounted on a mandrel 2, which is secured to the chuck 3 by the usual means.

The chuck rotates in theheadstock 4 and the mandrel 2 is carried at the other end on a centre or other type bearing in the tailstock 6.

disengagement of the detent is of very short duration. The gears 2| and 22 are so chosen that one'revolution of shaft 20 produces an angular The tool I is carried on a slide 8 which is capable of rectilinear motion on guides 9 in the saddle I9, the motion being at right angles to and radial to the axis it about which the saddle rotates. The latter is capable of rotation on the circular guides II in the saddle I2 which in turn is displaced transversely to the axis of the work'along I guides I3 on the saddle I4 which is mounted on the bed I5 of the machine.

By these provisions the tool I is capable of moving about the axis I6 of the circular guides II and moving radially to the axis IS, the latter motion being for the purpose of producing simultaneously relief on both flanks and the periphery of: the hob teeth, and can be accomplished-by anyof the means commonly employed on relieving lathes; Means are provided for producing three motions, namely,

rotation of the work on its own axis'and two motions of the tool in a plane containing the axis of the work one motion arcuate about acenter which lies at or on the opposite side of the axis of the work and the other an intermediate to and fro motionradial to thecenter of the arcuate motion, ,the mechanization producing these three motions being interconnected to bring them into proper corelation as regards extent and sequence.

; .For the purpose of producing a hob of the form required it is necessary that the tool should be given anintermittent rotary motion about the axis I6, this motion being a certain slight fixed amount, every time the work I rotates through That.

is to say, if, as shown in Figure 7, the hob has sixteen flutes, the slight intermittent rotary motion 7 of the tool about the axis I6 must occur everysixteenth of a revolution of the work I. The drive for this intermittent motion i in this case froIn-the chuck 3 through gears I8 and is transmitted to theworm I9 through shaft 20 and thegears ZI, 22,1g3,.z4,25, zc, 21, 28, 29 and so. The g'eartll is secured to the shaft 6| to which the worm. I9 is secured andwhich is carried in:

bearings ,53'attached to saddle I2. The worm engages worm wheel teeth 62 in the sector 64 integral wither attached to saddle I0.

1 jThejjfrequency of the intermittent movements of the tool! about the axis l6, per revolution'of the work I, isobtained by the ratio of the gears 2i 22.;jThe intermittent motion is produced by the apparatus in casing The shaft 20 drives:

' movementof wheel 22 equal to the angular pitch tion. The retraction of the detent, however, is

of such short duration that before cam 32 is moved to the next stop 39 the detent has reengaged the periphery of the cam and prevents it from passing beyond the next stop.

As already stated the relieving may be accomplished by any of the well known means. In the present instance a series of gears 40 interconnects the shaft 26 and shaft M at the appropriate speed and the latter, passing longitudinally through bed [5 of the machine, as shown in Figures 5 and 7-10, drives through bevels 42, gears 43, 44, 45, the vertical-shaft 46 and gears 41, the cam 48. The latter moves the saddle 8 on guides 9 against the action of a spring (not shown) which retracts saddle 8 at the end of each revolution of cam 48.

Inthe drawing the axis I6 about which the tool rotates passes through, the axis of rotation of the work so that the hob produced corresponds toa pinion of the same radius as the hob. The radius on which the hob teeth lie, however, in a plane through the axis of the hob, can be made greater or less, irrespective of the hob diameter, by moving the saddle I2 transversely untilthe axis I6 lies at the appropriate distance from the h-ob teeth to make the latter lie on an arc of the required radius. In order to accommodate this translation the idler 44 interconnecting gears 43 and 45, is moved round the are 49 in the supporting frame 50. v 28, 29, is swung round to enable these gears 28, 29, to re-engage gears 21, 30.

In order. to manufacture hobs with difierent numbers .of flutes without modification to the gears 2|, 22, and index-ing cam 32, the gears I8 can. be changed'to vary the speed of the shaft 20 in relation to the speed of the work I, and in order to vary the amount of angular movements of the tool aboutthe axis I6 the gears 23, 24, can be changed to vary the relation between the motion of the indexing cam 32 and the worm I 9.

"In'the machine as above described while the cutting edges of the hob produced will lie in the tooth will be'symmetrical about a circumferential 3 line. If desired the body of each tooth can be made symmetric-a1 about the helical path 7' by giv-.

ing the saddle .8 on which the tool I is carried a slight continuous}longitudinal movement during the formation of each tooth.

profile cutter but it may be any tool, for example, a profile grinder.

There is no axial motion of a saddle when producing the hob. Apart from the reciprocating.

movement of. the slide to give simultaneous flank and peripheralrelief'to thehob teeth, which is a b, the same in bbth'cases, when cutting the conven- The arm 5| supporting the gears.

tional hob the work has rotary motion and the tool axial motion, while in cutting hobs by means of machines embodying the present invention the work has rotary motion and thetool has a rotary motion, only about the axis on which the saddle I0 rotates.

While the end to end motion of the tool 1 and the to and fro relieving motion of the tool are normally in a plane containing the axis of the work and this is the theoretically correct plane in which they should operate, a slight departure from this plane will have such a small effect on the accuracy of the work that for practical purposes it would produce a satisfactory result.

We claim:

1. A machine for producing a hob for cutting internally projecting gear teeth of concave involute form, comprising a lathe slide rest, cross slide thereon, a saddle associated with saidcross slide, a circular guide for said saddle, a tool holder carried on said saddle, the cross slide being adjustable to locate the axis of movement of the saddle as guided by the circular guide in a position intersecting the axis out rotation of the lathe or on the far side thereocf with reference to the tool holder, means for imparting intermittent rotary motion to said saddle proportional to the rotation of the work between cuts on successive hob teeth and means for relieving both sets of flanks of hob teeth simultaneously with the production of peripheral relief for said teeth, the last said means comprising means for moving the tool radially toward and away from the axis of rotation of the saddle.

2. A machine as claimed in claim 1 wherein the tool comprises an ordinary profile cutter.

3. A machine as claimed in claim 1 wherein the tool comprises a profile grinder.

STANLEY SMITH COOK.

LOUIS MORTIMER DOUGLAS.

REFERENCES CITED I The following references are of record in the file of this patent:

UNITED STATES PATENTS 

